Make dart2js unittests async.

tests/compiler/dart2js/array_static_intercept_test.dart

Index: tests/compiler/dart2js/array_static_intercept_test.dart
diff --git a/tests/compiler/dart2js/array_static_intercept_test.dart b/tests/compiler/dart2js/array_static_intercept_test.dart
index 23e88eb4ffb0b04f0bfb3b7c1587482c4c71faab..d53e10b10a5b59faf025855f826e67a15f92f5bc 100644
--- a/tests/compiler/dart2js/array_static_intercept_test.dart
+++ b/tests/compiler/dart2js/array_static_intercept_test.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import "package:expect/expect.dart";
+import 'package:expect/expect.dart';
+import 'package:async_helper/async_helper.dart';
 import 'compiler_helper.dart';
 
 const String TEST_ONE = r"""
@@ -14,8 +15,9 @@ foo(a) {
 """;
 
 main() {
-  String generated = compile(TEST_ONE, entry: 'foo');
-  Expect.isTrue(generated.contains(r'.add$1('));
-  Expect.isTrue(generated.contains(r'.removeLast$0('));
-  Expect.isTrue(generated.contains(r'.length'));
+  asyncTest(() => compile(TEST_ONE, entry: 'foo', check: (String generated) {
+    Expect.isTrue(generated.contains(r'.add$1('));
+    Expect.isTrue(generated.contains(r'.removeLast$0('));
+    Expect.isTrue(generated.contains(r'.length'));
+  }));
 }